An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Project Orion

Whilst browsing the videos on Dr. Buzzo’s YouTube channel, I came across a nice one – a segment from Carl Sagan’s legendary television series Cosmos talking about interstellar spaceflight, and the technologies we could use to achieve interplanetary manned spaceflight.

Now, maybe I just read too much Carl Sagan works, but I happen to get a little bit passionate about such things.

Now, something important to note: Every technology, with one single exception, that of a large enough solar sail, that has ever been seriously considered or developed by humanity as the means to send a manned spacecraft beyond our solar system, or even to the outer part of our solar system, utilizes some form of nuclear engineering as its energy source.

But nuclear engineering – fission reactors, fusion reactors, or bomb-like nuclear pulse propulsion – does give us the means to do it, where no other energy systems can.

A spacecraft capable of manned interstellar travel would, in my opinion, be the most fantastic triumph of human engineering ever devised. Something fantastic, at the limits of human imagination. And such technology already exists. We simply lack the political fortitude to use it.

It’s quite depressing, almost, to note that we have the means to travel to other stellar systems, and colonize and live there, in all likelihood, well within a human lifetime, but we do not. Not because our science precludes it, our our technology, or our vision, or our intelligence, or our wealth preclude it, but because politicians preclude it.

Now, after watching this video, I happened across another very, very good video on YouTube:

5 Responses

In all fairness, the amount of fissile material required for a manned interstellar flight using nuclear-pulse propulsion is non-trivial- Freeman Dyson did some preliminary calculations on the subject back in the mid-1960s and found that it would take a considerable proportion of the accessible fissile material in the entire solar system (although I have no idea what they thought that figure was for the Sol system back in 1965). Besides, we need to build something like the Interstellar Planet Finder and locate some kind of habitable planet first.

But nuclear-pulse propulsion has a lot of potential for manned travel within the solar system as well. It could make it possible to transport a whole colony group to Mars, for example, using relatively near-term technology, and using amounts of nuclear fuel that we can produce using existing infrastructure. But sadly, I have a really hard time imagining governments ever actually pursuing this technology– especially since current trends are working against manned space flight.

If you haven’t read it, I heartily recommend George Dyson’s book on Project Orion.

For interstellar travel, I’m sure the use of deuterium-tritium fusion – even using current, mature technology, i.e. what is essentially a Teller-Ulam bomb – is the way to go, rather than using fission.

Well, the problem there is that you need to detonate it somehow (i.e., fission primaries)- and also that tritium is rare and consequently expensive. I think that the British Interplanetary Society did a study about thirty years ago of thermonuclear pulse propulsion for interstellar travel, but I think it used some sort of exotic laser detonation system.

The most economical concept I’ve seen for pulse propulsion is antimatter-initiated fusion. This requires a supply of frozen deuterium pellets and a small supply of antimatter (thankfully, since antimatter is extremely energy intensive to make). A pellet is ejected into the pulse explosion zone and a microgram (? or less?) quantity of antimatter sent to intercept it there. The matter/antimatter total destruction produces an energy release which initiates a fusion explosion in the deuterium pellet.

All theoretical, immense practical challenges to overcome, but very interesting.

Might it be more economical with fuel to take the process you describe and do it on a (much) smaller scale within some kind of magnetic nozzle, with more detonations? That way more of the momentum from the detonations would be imparted to the spacecraft. You could also potentially manipulate the magnetic field to increase fuel compression before ignition.